The present invention generally relates to a vehicle control apparatus and particularly related to a vehicle control apparatus in which when the control apparatus is tested, the setting contents of a specification change-over means in the control apparatus can be checked from outside of the control apparatus regardless of control logic.
Recently, a variety of vehicle control apparatuses using microcomputers have become popular to use. As an example of such a vehicle control apparatus, an engine air-fuel ratio control apparatus comprising operational blocks corresponding to a CPU (central processing unit), an RAM (random access memory), an ROM (read only memory), an A/D (analogue-to-digital) converter, an I/O (input/output) unit, etc. is disclosed in "Automobile Technology" Vol. 38, No. 2, 1984, page 158.
A variety of control specifications are required for such engine control apparatuses in accordance with the kind of vehicle, (with which it is assiciated)the kind of engine capacity, the kind of transmission, and so on, and a demand for various kinds of engine control apparatuses which can satisfy various requirements has become stronger and stronger.
In order to respond to such a demand, it is possible to consider an engine control apparatus arranged such that a variety of demand control specifications, in other words, various control data and control logic, are stored in advance in an ROM provided in the engine control apparatus and one of many possible demand control specifications is selected on a basis of selection data applied to an input port of a microcomputer or the like in the engine control apparatus.
When the thus arranged control apparatus is tested individually or as a unit, it is necessary to test whether the control apparatus can function correctly or not from outside thereof, through terminals of the control apparatus.
For example, in some cases, a test can be made only through a connector to which an outside connector can be connected from outside of the apparatus, after a control circuit printed on a substrate has been received in a housing and the parts number for identification has been indicated on the housing.
In such cases, in order to judge which one of the control specifications stored in the ROM in the control apparatus is selected, it is necessary to make the judgement on the bases of an externally inspected difference in operation as a difference in control specification. In order to identify the kind of a control apparatus among a variety of control apparatuses in which the respective specifications are varied from one another in control data, however, there have often been difficulties in a correct execution of the test. For, example, typically the method of test has been complicated, thus, resulting in a long time has been taken for the test, etc.
In those cases, however, there is a case where ROMs which have been subject to unit test in advance are used in the control apparatuses and the operation of various input/output terminals of the control apparatuses can be tested in a short time regardless of the partial variations in control specifications, and therefore a difficulty is only in distinguishing the partial variations in control specifications.
For example, in a case where the control data is different between two kinds of controls apparatuses only in the points that two kinds of the control apparatuses have time data of 10 minutes and 20 minutes respectively, there has been a problem that it is impossible to distinguish the kind of a control apparatus unless the control apparatus is caused to operate for at least 10 minutes and therefore it takes a very long time for execution of the test. The difficulty has been a serious problem in mass-production of control apparatuses.